Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$18.57	10.705%	$20.5579	$20.56	$20.55	$20.60
Purchase #2	$43.59	8.376%	$47.2411	$47.24	$47.25	$47.20
Purchase #3	$141.89	6.485%	$151.0916	$151.09	$151.10	$151.10
Purchase #4	$153.85	4.327%	$160.5071	$160.51	$160.50	$160.50
Purchase #5	$212.82	7.390%	$228.5474	$228.55	$228.55	$228.50
Purchase #6	$229.72	6.339%	$244.282	$244.28	$244.30	$244.30
Purchase #7	$162.88	13.124%	$184.2564	$184.26	$184.25	$184.30
7 purchase totals =	$963.32		$1,036.4835	$1,036.49	$1,036.50	$1,036.50